1. Technical Field
The present invention generally relates to an application specific integrated circuit (ASIC) design and a messaging technique. More particularly, the present invention is directed to an ASIC design which eliminates the need for a microprocessor, and a message frame design and messaging technique for controlling remote devices which are connected to an SAE J1850 serial communication data bus within an automotive vehicle.
2. Discussion
Automotive vehicles are commonly equipped with multiple-access serial data communications networks to enable data transfer between various electronic components within the vehicle. The Society of Automotive Engineers (SAE) has established the J1850 class data communications network which has become widely accepted throughout the automotive industry. The J1850 standard is a set of technical requirements and parameters which specify the use of symbols for communicating serial data over a one or two-wire communications bus.
The J1850 protocol is based on a medium-speed (Class B) serial multiplex communication protocol for use in automotive vehicles. Serial multiplex communication (MUX) is a method of reducing wiring requirements while increasing the amount and type of data which may be shared between various electronic components connected to the communication network. This technique is achieved by connecting each component, or node, to a serial bus, consisting of either a single wire or a twisted pair of wires. Each node collects whatever data is useful to itself or other nodes (i.e. wheel speed, engine rpm, oil pressure, etc.), and then transmits this data onto the J1850 bus, where any other node which needs this data can receive it. The result of data sharing is reduced wiring and eliminating the need for redundant sensing systems.
In one exemplary implementation, one or more microprocessor based controllers are positioned throughout the vehicle and communicate with each other along the J1850 data bus. Each controller will periodically transmit information in the form of message data organized into a single message frame. This transmission can take place once the controller determines that the data bus is free. Once this message frame is transmitted onto the J1850 bus, this information is available to either a specific node, such as another controller, or all of the nodes on the data bus depending on the type of messaging scheme implemented.
An additional feature of the J1850 protocol allows one or more of the nodes to respond to the original data message within the same message frame (i.e. within a short period of time after receiving the original message, but before another node begins transmitting a new message frame). Within the J1850 protocol, this is referred to as an “in-frame response” (IFR). Accordingly, the J1850 protocol design provides a single wire network through which information can be exchanged between various controllers connected to the data bus. For example, the engine controller and the transmission controller may exchange information via the J1850 data bus concerning real-time operating or performance conditions of their associated systems.
The current J1850 system is limited to broadcasting data, and is not designed for the transmission of specific executable commands to the remote nodes on the data bus. However, rather than just broadcasting or exchanging information, it is desirable to use a messaging scheme on the J1850 bus in which a message containing a specific command is sent by the controller to a receiving node for controlling or executing various operations performed by the receiving node. Once the message is received and the command executed, the receiving node may respond using the in-frame response as to whether the command was successfully executed, or the outcome of the command execution. Currently, the aforementioned control and feedback technique is not implemented.
Accordingly, it is desirable to provide a messaging scheme which allows executable command information to be contained within a message frame, and allow a receiving node to provide an in-frame response within the same message frame as feedback to the controller. Further, it is desirable to provide a receiving node for performing various control functions in response to the command information contained within the message frame. It is also desirable to provide a sub ID scheme which allows a receiving node to identify the type of executable command information, or the type of command message contained within the message frame. Moreover, it is desirable to provide a receiving node which eliminates the need for a microprocessor, and thus the need for writing and testing additional computer code for operating the microprocessor. Finally, it is contemplated that the receiving node may also communicate with various smart drivers connected to the receiving node for controlling various electrical components, and gathering feedback data from the electrical components.